Electronic device

ABSTRACT

An electronic device includes a housing and a circuit board contained in the housing. The housing includes a main wall, a side wall, a vertical wall, a first rib, and a second rib. The side wall is integrally formed with the main wall. The vertical wall is integrally formed with the main wall and faces to the side wall. The first rib is integrally formed with the side wall and the main wall. The first rib extends from the side wall toward the vertical wall. The first rib has a first end portion separated from the vertical wall. The second rib is integrally formed with the vertical wall and the main wall. The second rib extends from the vertical wall toward the side wall. The second rib has a second end portion separated from the side wall. The second rib faces to the first end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2005-132077, filed Apr. 28, 2005, theentire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates to an electronic device including ahousing provided with a reinforcing structure.

2. Description of the Related Art

A housing for an electronic device such as a portable computer isreinforced to enhance strength.

As one example of a reinforcing structure, there is a structure in whicha plurality of ribs are formed on a peripheral wall of the housing. Theribs extend inwards from the peripheral wall. The plurality of ribs areformed on a part or the substantially whole of the peripheral wall. Thestrength of the housing is enhanced by the structure including the ribs.

On the other hand, when an impact is exerted on the housing, it iscracked by the impact. When a crack is formed in this manner, thehousing absorbs the impact. The absorption of the impact inhibits thetransmission of the impact to a PCB (printed circuit board) and the likestored in the housing.

However, in a case where the housing has such a reinforcing structure asdescribed above, it is considered that when the high impact is exerted,the crack is formed in a broad region to connect tips of the ribs whileavoiding the ribs. When the crack is formed in the broad region, thehousing unfavorably looks bad.

Therefore, there is proposed a reinforcing structure in which the ribsextend from a region of the peripheral wall to be provided with the ribsto a vertical wall facing the region and formed in the housing, therebyfurther enhancing the strength of the housing. This type of reinforcingstructure is disclosed in Jpn. Pat. Appln. KOKAI Publication No.4-280518. The further enhancement of the strength of the housinginhibits the formation of the crack in the housing.

However, in the reinforcing structure disclosed in Jpn. Pat. Appln.KOKAI Publication No. 4-280518, the further enhancement of the strengthof the housing difficulty in absorbing the exerted by the peripheralwall. Therefore, when the high impact is exerted on the peripheral wall,it is considered that the high impact is transmitted to a component suchas a PCB without being absorbed by the housing.

When the impact is transmitted to a component such as the PCB in thismanner, a function of the component is liable to be destroyed.Therefore, it is not preferable that the impact is transmitted to acomponent such as the PCB without being absorbed by the housing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A general architecture that implements the various feature of theinvention will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrateembodiments of the invention and not to limit the scope of theinvention.

FIG. 1 is a perspective view of a portable computer in a firstembodiment of the present invention;

FIG. 2 is an exploded perspective view of a first housing shown in FIG.1;

FIG. 3 is a perspective view showing the inside of an upper cover shownin FIG. 2;

FIG. 4 is a perspective view showing an enlarged region of F4 shown inFIG. 3;

FIG. 5 is a plan view of the region of F4 shown in FIG. 3;

FIG. 6 is a sectional view cut along line the F6-F6 shown in FIG. 5;

FIG. 7 is a sectional view cut along the line F7-F7 shown in FIG. 5;

FIG. 8 is a plan view showing an arrangement relation between first andsecond ribs of a portable computer in a second embodiment of the presentinvention;

FIG. 9 is a plan view showing an arrangement relation between the firstand second ribs of a portable computer in a third embodiment of thepresent invention;

FIG. 10 is a plan view showing an arrangement relation between the firstand second ribs of a portable computer in a fourth embodiment of thepresent invention;

FIG. 11 is a plan view showing an arrangement relation between the firstand second ribs of a portable computer in a fifth embodiment of thepresent invention;

FIG. 12 is a plan view showing an arrangement relation between the firstand second ribs of a portable computer in a sixth embodiment of thepresent invention;

FIG. 13 is a perspective view showing the inside of an upper cover of aportable computer in a seventh embodiment of the present invention; and

FIG. 14 is a perspective view showing the inside of an upper cover of aportable computer in a seventh embodiment of the present invention.

DETAILED DESCRIPTION

Various embodiments according to the invention will be describedhereinafter with reference to the accompanying drawings. In general,according to one embodiment of the invention, an electronic deviceincludes a housing and a circuit board contained in the housing. Thehousing includes a main wall, a side wall, a vertical wall, a first rib,and a second rib. The side wall is integrally formed with the main wall.The vertical wall is integrally formed with the main wall. The verticalwall faces to the side wall. The first rib is integrally formed with theside wall and the main wall and extends from the side wall toward thevertical wall. The first rib has a first end portion separated from thevertical wall. The second rib is integrally formed with the verticalwall and the main wall and extends from the vertical wall toward theside wall. The second rib has a second end portion separated from theside wall. The second rib faces to the first end portion.

As one example of an electronic device in a first embodiment of thepresent invention, a portable computer 10 will be described withreference to FIGS. 1 to 7.

FIG. 1 shows the portable computer 10. As shown in FIG. 1, the portablecomputer 10 includes a computer main body 20 and a display unit 30.

The computer main body 20 includes a first housing 21 and a circuitboard 300. The first housing 21 is one example of a housing which isreferred to in the present invention. The first housing 21 has a flatbox shape. Components such as a hard disk are contained in the firsthousing 21.

FIG. 2 shows an exploded state of the first housing 21. As shown in FIG.2, the first housing 21 includes an upper cover 22 and a lower cover 23.The upper cover 22 constitutes an upper part of the first housing 21.The lower cover 23 constitutes a lower part of the first housing 21. Thefirst housing 21 is formed by superimposing the upper cover 22 and thelower cover 23 on each other.

The upper cover 22 opens downwards. The upper cover 22 is formed of, forexample, a magnesium alloy. Note that the material forming the uppercover 22 is not limited to the magnesium alloy. For example, the uppercover 22 may be formed of another metal. The upper cover 22 may beformed of a resin.

The upper cover 22 has an upper wall 22 a, an upper front wall 22 b, anupper left wall 22 c, an upper right wall 22 d, and an upper rear wall22 e. The upper wall 22 a is one example of a main wall mentioned in thepresent invention. A keyboard 24 is disposed on the upper surface of theupper wall 22 a.

The upper front wall 22 b is integrally formed on a front edge of theupper wall 22 a, and extends downwards. The upper left wall 22 c isintegrally formed on a left edge of the upper wall 22 a, and extendsdownwards. The upper right wall 22 d is integrally formed on a rightedge of the upper wall 22 a, and extends downwards. The upper rear wall22 e is integrally formed on a rear edge of the upper wall 22 a, andextends downwards. Each of the upper front wall 22 b, the upper leftwall 22 c, the upper right wall 22 d, and the upper rear wall 22 e isone example of the side wall mentioned in the present invention.

A structure of the upper cover 22 will be described later in detail.

The lower cover 23 opens upwards. The lower cover 23 has a lower wall 23a, a lower front wall 23 b, a lower left wall 23 c, a left right wall 23d, and a lower rear wall 23 e. The lower wall 23 a is one example of anmain wall mentioned in the present invention.

The lower front wall 23 b is integrally formed on a front edge of thelower wall 23 a, and extends upwards. The lower left wall 23 c isintegrally formed on a left edge of the lower wall 23 a, and extendsupwards. The lower right wall 23 d is integrally formed on a right edgeof the lower wall 23 a, and extends upwards. The lower rear wall 23 e isintegrally formed on a rear edge of the lower wall 23 a, and extendsupwards.

Each of the lower front wall 23 b, the lower left wall 23 c, the lowerright wall 23 d, and the lower rear wall 23 e is one example of the sidewall mentioned in the present invention.

As shown in FIG. 1, the upper front wall 22 b is superimposed on thelower front wall 23 b in a vertical direction to form a front wall 21 bof the first housing 21. The upper left wall 22 c is superimposed on thelower left wall 23 c in the vertical direction to form a left wall 21 cof the first housing 21. The upper right wall 22 d is superimposed onthe lower right wall 23 d in the vertical direction to form a rightwall21 d of the first housing 21. The upper rear wall 22 e is superimposedon the lower rear wall 23 e in the vertical direction to form a rearwall 21 e of the first housing 21.

As shown in FIG. 2, The circuit board 300 includes a substrate 301 andsome circuit components 302. The some circuit components 302 are mountedon the substrate 301. The circuit board 300 is contained in the firsthousing 21.

As shown in FIGS. 1 and 2, portions in the vicinity of a left frontcorner portion 25 of the first housing 21, specifically the portions onthe sides of the left wall 21 c and the front wall 21 b via the cornerportion 25 extend outwards to form a protruding portion 25 a.

Portions in the vicinity of a right front corner portion 26,specifically the portions on the sides of the right wall 21 d and thefront wall 21 b via the corner portion 26 extend outwards to form aprotruding portion 26 a. Portions in the vicinity of a left rear cornerportion 27, specifically the portions on the sides of the left wall 21 cand the rear wall 21 e via the corner portion 27 extend outwards to forma protruding portion 27 a. Portions in the vicinity of a right rearcorner portion 28, specifically the portions on the sides of the rightwall 21 d and the rear wall 21 e via the corner portion 28 extendoutwards to form a protruding portion 28 a.

These protruding portions 25 a, 26 a, 27 a, and 28 a extend outwardlyfrom portions other than the protruding portions 25 a, 26 a, 27 a, and28 a in the first housing 21.

Therefore, the upper cover 22 and the lower cover 23 in the vicinity offour corners extend outwardly, which correspond to the respectiveprotruding portions 25 a, 26 a, 27 a, and 28 a.

As shown in FIG. 1, the display unit 30 is provided with a secondhousing 31 and a liquid crystal display panel 32. The liquid crystaldisplay panel 32 is stored in the second housing 31. The liquid crystaldisplay panel 32 has a screen 32 a to display an image. The screen 32 ais exposed outwardly from the second housing 31 through an opening 31 aformed in the front surface of the second housing 31.

The second housing 31 is supported on a rear end portion of the firsthousing 21 via a hinge (not shown). The display unit 30 is rotatablebetween a closed position and an opened position. In the closedposition, the display unit 30 is laid on the computer main body 20 tocover the keyboard 24 from above. In the opened position, the displayunit 30 stands with respect to the computer main body 20 to expose thekeyboard 24 and the screen 32 a.

The first housing 21 is provided with a reinforcing structure against animpact at a time when, for example, the portable computer 10 falls. Thisreinforcing structure for the upper cover 22 will be describedrepresentatively.

FIG. 3 shows the inside of the upper cover 22. As shown in FIG. 3, inthe upper cover 22, the protruding portion 27 a in the vicinity of theleft rear corner portion 27, and the protruding portion 28 a in thevicinity of the right rear corner portion 28 are provided with thereinforcing structure.

FIG. 4 enlarges and shows a region of F4 shown in FIG. 3. As shown inFIG. 4, a boss portion 43 is formed in the corner portion 28 of theupper cover 22. The boss portion 43 passes, for example, a bolttherethrough to fasten the upper cover 22 and the lower cover 23 to eachother in a case where they are assembled.

The boss portion 43 extends downwards from the inner surface of theupper wall 22 a. Note that FIG. 4 shows that the inside of the uppercover 22 opens upwards. Therefore, it is shown that the boss portion 43extends upwards. The boss portion 43 has a substantially columnar shape.

Moreover, an inner portion of the upper cover 22 facing the upper rightwall 22 d in the region of the protruding portion 28 a is provided witha protrusion 45 for use in arranging various components such as the PCBin the first housing 21. The protrusion 45 is integrally formed with theupper wall 22 a. A vertical wall 46 facing the upper right wall 22 d isformed between the protrusion 45 and the boss portion 43. The verticalwall 46 is integrally formed with the upper wall 22 a.

A wall surface 45 a of the protrusion 45 facing the upper right wall 22d and a wall surface 46 a of the vertical wall 46 facing the upper rightwall 22 d are positioned, for example, on substantially the same plane.

As the reinforcing structure, the protruding portion 28 a is providedwith a plurality of first ribs 51 and a plurality of second ribs 52.

Among the plurality of first ribs 51, two first ribs 51 are formed in aninner region of the protruding portion 28 a in the upper right wall 22d. One of the first ribs 51 formed in the upper right wall 22 d isformed in a first point 53 facing the protrusion 45 in the upper rightwall 22 d.

The other first rib 51 is formed in a second point 54 between the bossportion 43 and the vertical wall 46 in the upper right wall 22 d. Thefirst point 53 is positioned in front of the second point 54.

The first ribs 51 formed in the first and second points 53 and 54 extendinwardly along a direction A from the upper right wall 22 d toward theupper left wall 22 c, and are substantially parallel to each other.

FIG. 5 is a plan view of the region of F4 shown in FIG. 3. As shown inFIG. 5, the first ribs 51 formed in the first and second points 53 and54 of the upper right wall 22 d extend from an intermediate point 55toward the protrusion 45 and the vertical wall 46, between theprotrusion 45 and vertical wall 46 and the upper right wall 22 d.

Tips of the first ribs 51, or a first end portion 400, formed in thefirst and second points 53 and 54 do not reach the protrusion 45 and thevertical wall 46. A length of each of the first ribs 51 formed in thefirst and second points 53 and 54 is one example. That is, the first endportion 400 is separated from the protrusion 45 and the vertical wall46. The first ribs 51 do not reach the vertical wall such as theprotrusion 45 or the vertical wall 46.

The lengths of the first ribs 51 formed in the first and second points53 and 54 are determined depending on a strength required for theprotruding portion 28 a. Rigidity of the region in the vicinity of thefirst rib 51 in the upper right wall 22 d enhances, when each first rib51 lengthens.

An impact input from the side of the upper right wall 22 d deforms ordestroys, for example, the upper wall 22 a, and is accordingly absorbed.The first ribs 51 formed in the first and second points 53 and 54 areprovided with predetermined lengths to secure the strength of the firsthousing 21. Moreover, the first ribs 51 do not reach the protrusion 45or the vertical wall 46. Deformation and destruction described abovetakes place between the first ribs 51 on the one hand, and theprotrusion 45 and vertical wall 46, on the other hand. That is, openingsbetween the first member 51 and the protrusion 45, or, between the firstmember 51 and the vertical wall 46 function as a deformation ordestruction tolerance.

FIG. 6 is a sectional view cut along line F6-F6 shown in FIG. 5. Asshown in FIG. 6, a height H1 of the first rib 51 formed in the firstpoint 53 is larger than a thickness H2 of the upper wall 22 a in thevicinity of the first point 53. That is, H1>H2.

Similarly, the height of the first rib 51 formed in the second point 54is set to be larger than the thickness of the upper wall 22 a in thevicinity of the second point 54.

FIG. 7 is a sectional view cut along line F7-F7 shown in FIG. 5. Asshown in FIG. 7, a side surface shape of the first rib 51 formed in thefirst point 53 of the upper right wall 22 d is, for example, asubstantially rectangular shape. Therefore, the height H1 of the firstrib 51 formed in the first point 53 is larger than H2 in the wholeregion.

The side surface shape of the first rib 51 formed in the second point 54is substantially similar to that of the first rib 51 formed in the firstpoint 53. Therefore, the height of the first rib 51 formed in the secondpoint 54 is larger than the thickness of the upper wall 22 a in thevicinity of the point where the first rib 51 is formed in the wholeregion.

Note that the side surface shapes of these first ribs 51 are not limitedto the substantially rectangular shapes. For example, the side surfaceshape of the first rib 51 may be trapezoidal. In this case, the heightof the lowest portion of the first rib 51 may be larger than thethickness of the upper wall 22 a in the vicinity of the point providedwith the first rib 51.

As shown in FIGS. 6 and 7, the first ribs 51 formed in the first andsecond points 53 and 54 are formed integrally with the upper wall 22 aand the upper right wall 22 d.

As shown in FIG. 4, among the plurality of second ribs 52, one of secondrib 52 is formed integrally with the protrusion 45 and the upper wall 22a. Therefore, the protrusion 45 functions as a vertical wall mentionedin the present invention. As described above, the existing protrusion 45or the like may be utilized as the vertical wall.

The second rib 52 formed on the protrusion 45 extends from the wallsurface 45 a facing the upper right wall 22 d toward the upper rightwall 22 d. The second rib 52 formed on the protrusion 45 is disposed infront of the first rib 51 formed in the first point 53.

The second rib 52 formed on the protrusion 45 extends substantially inparallel with the first ribs 51 formed in the first and second points 53and 54 toward the upper right wall 22 d.

The second rib 52 formed on the protrusion 45 is formed integrally withthe protrusion 45 and the upper wall 22 a like the first ribs 51 formedin the first and second points 53 and 54.

The height of the second rib 52 formed on the protrusion 45 is largerthan the thickness of the upper wall 22 a in the vicinity of the pointwhere the second rib 52 is formed in the same manner as in the firstribs 51 formed in the first and second points 53 and 54.

Among the plurality of second ribs 52, another second rib 52 is formedintegrally with the vertical wall 46 and the upper wall 22 a. As shownin FIGS. 4 and 5, the second rib 52 extends from the wall surface 46 afacing the upper right wall 22 d toward the upper right wall 22 d in thevertical wall 46.

The second rib 52 formed on the vertical wall 46 is disposed between thefirst ribs 51 formed in the first and second points 53 and 54, andextends substantially in parallel with the first ribs 51 formed in thefirst and second points 53 and 54. The vertical wall 46 is one exampleof the vertical wall mentioned in the present invention.

The second rib 52 formed on the vertical wall 46 is formed integrallywith the vertical wall 46 and the upper wall 22 a in the same manner asin the first ribs 51 formed in the first and second points 53 and 54.

The height of the second rib 52 formed on the vertical wall 46 is largerthan the thickness of the upper wall 22 a in the vicinity of the secondrib 52.

The side surface shapes of the second ribs 52 formed on the protrusion45 and the vertical wall 46 are, for example, substantially rectangularshapes in the same manner as in the first ribs 51 formed in the firstand second points 53 and 54. Moreover, the heights of these second ribs52 are larger than the thickness of the upper wall 22 a in the vicinityof the second ribs 52 in the substantially whole region. The sidesurface shape of the second rib 52 is not limited to the substantiallyrectangular shape in the same manner as in the first ribs 51 formed inthe first and second points 53 and 54.

The first ribs 51 formed in the first and second points 53 and 54, thesecond rib 52 formed on the protrusion 45, and the second rib 52 formedon the vertical wall 46 are disposed, for example, apart from oneanother at an substantially equal interval along a direction D1 in whichthese ribs are arranged. The arrangement direction D1 is substantiallylinear.

Tips of the second ribs 52, or a second end portion 500, formed in theprotrusion 45 and the vertical wall 46 do not reach the upper right wall22 d. A length of each of the second ribs 52 formed in the protrusion 45and the vertical wall 46 is one example. That is, the second end portion500 is separated from the upper right wall. The second ribs 52 do notreach the side wall such as the upper right wall 23 d.

An impact input from the side of the upper right wall 22 d deforms ordestroys, for example, the upper wall 23 a, and is accordingly absorbed.The second ribs 52 formed in the protrusion 45 and the vertical wall 46are provided with predetermined lengths to secure the strength of thefirst housing 21. Moreover, the second ribs 52 do not reach the upperright wall 22 d. Deformation and destruction described above takes placebetween the second ribs 52 on the one hand, and the upper right wall 22d, on the other hand. That is, openings between the second ribs 52 andthe upper right wall 22 d function as a deformation or destructiontolerance.

There will be specifically described an arrangement relation among thefirst ribs 51 formed in the first and second points 53 and 54, thesecond rib 52 formed on the protrusion 45, and the second rib 52 formedon the vertical wall 46. A distance from the first rib 51 formed in thesecond point 54 to the second rib 52 formed on the vertical wall 46, adistance from the second rib 52 formed on the vertical wall 46 to thefirst rib 51 formed in the first point 53, and a distance from the firstrib 51 formed in the first point 53 to the second rib 52 formed on theprotrusion 45 are substantially equal intervals.

The length of the second rib 52 formed on the protrusion 45 is set tohave an area C1 of the second rib 52 facing the first rib 51 formed inthe first point 53 along the arrangement direction D1.

The area C1 of the side surface of the second rib 52 formed on theprotrusion 45 facing the first rib 51 formed in the first point 53 isshown by slant lines. An area C2 of the first rib 51 formed in the firstpoint 53 facing the second rib 52 formed on the protrusion 45 is shownby slant lines.

As shown in FIG. 5, the facing areas C1 and C2 are determined dependingon the distance from the first rib 51 formed in the first point 53 tothe second rib 52 formed on the protrusion 45. This respect will bespecifically described.

As shown in FIG. 5, assuming that the distance from the first rib 51formed in the first point 53 to the second rib 52 formed on theprotrusion 45 is b1, and the length of each of the facing areas C1 andC2 is a1, a length L1 of the second rib 52 formed on the protrusion 45is determined to satisfy a1>b1/2.

A length L2 of the second rib 52 formed on the vertical wall 46 is setto have areas C3 and C4 facing the first ribs 51 formed in the first andsecond points 53 and 54, respectively. In FIG. 4, the areas C3 and C4 ofthe second rib 52 formed on the vertical wall 46 facing the first ribs51 in the first and second points 53 and 54 are shown by slant lines.

As shown in FIG. 5, the facing area C3 is determined depending on thedistance from the first rib 51 formed in the first point 53 to thesecond rib 52 formed on the vertical wall 46. This respect will bedescribed specifically.

Assuming that the distance from the first rib 51 formed in the firstpoint 53 to the second rib 52 formed on the vertical wall 46 is b2, andthe length of the facing area is a2, a length L2 of the second rib 52formed on the vertical wall 46 is determined to satisfy a2>b2/2.

Note that the first rib 51 formed in the first point 53 has an area C5similar to the area C3. Similarly, the first rib 51 formed in the secondpoint 54 has an area C6 similar to the facing area C4.

Furthermore, assuming that the length of the facing area C4 of thesecond rib 52 formed on the vertical wall 46 is a3, and the distancefrom the first rib 51 formed in the second point 54 to the second rib 52formed on the vertical wall 46 is b3, a length L2 of the second rib 52formed on the vertical wall 46 is determined to satisfy a3>b3/2.

That is, the length L2 of the second rib 52 formed on the vertical wall46 is determined to satisfy a2>b2/2 and a3>b3/2.

Note that in the present embodiment, the first ribs 51 formed in thefirst and second points 53 and 54, the second rib 52 formed on thevertical wall 46, and the second rib 52 formed on the protrusion 45 arearranged apart from one another at an equal interval. That is, b1=b2=b3.

Moreover, in the present embodiment, the lengths of the first ribs 51formed in the first and second points 53 and 54 are, for example, equalto each other. The length of the second rib 52 formed on the protrusion45 is, for example, equal to that of the second rib 52 formed on thevertical wall 46.

Therefore, in the present embodiment, when the length L2 of the secondrib 52 is determined to satisfy a2>b2/2, the length a3 of the facingarea C4 satisfies a3>b3/2.

Next, with reference to FIGS. 4 and 5, there will be described first andsecond ribs 51, 52 formed in the corner portion 28 and the upper rearwall 22 e among a plurality of first and second ribs 51, 52.

The upper right wall 22 d is gently bonded to the upper rear wall 22 ein the corner portion 28. A shape of a connection portion 56 whichconnects the upper right wall 22 d to the upper rear wall 22 e is, forexample, substantially circular.

Three first ribs 51 are formed on the connection portion 56 whichconnects the upper right wall 22 d to the upper rear wall 22 e in thecorner portion 28. These three first ribs 51 are formed in a third point57 positioned in front of the connection portion 56, a fourth point 58positioned rearward, and a fifth point 59 positioned between the thirdpoint 57 and the fourth point 58, respectively.

These three points 57, 58, and 59 are disposed, for example, apart fromone another at a substantially equal interval. Therefore, the respectivefirst ribs 51 formed in the three points 57, 58, and 59 are disposedapart at the substantially equal interval. The first ribs 51 formed inthese three points 57, 58, and 59 extend inwardly in the corner portion28. Since the boss portion 43 is formed substantially in the center ofthe corner portion 28, three first ribs 51 formed in the connectionportion 56 extend toward the boss portion 43.

These three first ribs 51 are formed integrally with the connectionportion 56 and the upper cover 22 in the same manner as in the firstribs 51 formed in the first and second points 53 and 54. The height ofeach of these three first ribs 51 is set to be larger than the thicknessof the upper wall 22 a in the vicinity of the point where each rib isformed. The side surface shapes of these three first ribs 51 aresubstantially rectangular in the same manner as in the first ribs 51formed in the first and second points 53 and 54.

Three second ribs 52 are formed on the boss portion 43. Three secondribs 52 formed on the boss portion 43 are formed on a facing surfaceportion 43 a facing the connection portion 56 in a peripheral surface ofthe boss portion 43. Therefore, the boss portion 43 functions as thevertical wall mentioned in the present invention.

As shown in FIG. 5, the three second ribs 52 formed on the boss portion43 are formed in a sixth point 60, a seventh point 61, and an eighthpoint 62 of the facing surface portion 43 a, respectively.

The sixth point 60 lies in front of the third point 57. The seventhpoint 61 faces a point between the third point 57 and the fifth point59. The eighth point 62 faces a point between the fifth point 59 and thefourth point 58. The sixth point 60, the eighth point 62, and theseventh point 61 are almost equidistantly apart.

The three second rib 52 formed on the boss portion 43 are formedintegrally with the boss portion 43 and the upper wall 22 a. The sidesurface shapes of three second ribs 52 formed on the boss portion 43 aresubstantially rectangular in the same manner as in the first ribs 51formed in, for example, the first and second points 53 and 54. Theheights of three second ribs 52 formed on the boss portion 43 are set tobe larger than the thicknesses of the upper wall 22 a in the vicinity ofthe points where the respective ribs are formed, respectively.

The second rib 52 formed in the sixth point 60 extends toward a frontportion of the first rib 51 formed in the third point 57. The second rib52 formed in the seventh point 61 extends between the first ribs 51formed in the third and fifth points 57 and 59. The second rib 52 formedin the eighth point 62 extends toward the first ribs 51 formed in thefourth and fifth points 58 and 59.

The first and second ribs 51, 52 formed in the corner portion 28 arearranged in a substantially circular form, and are disposed apart fromone another at equal intervals. As shown by a one-dot chain line in FIG.4, a direction D2 in which the first and second ribs 51, 52 formed inthe corner portion 28 are arranged is substantially circular.

As shown in FIG. 5, the lengths of the first and second ribs 51 and 52formed in the third and sixth point 57 and 60 are set so that thesefirst and second ribs 51, 52 have areas C7, C8 facing each other alongthe arrangement direction D2. The facing area C7 is disposed in thesecond rib 52 formed in the sixth point 60. The facing area C8 isdisposed in the first rib 51 formed in the third point 57.

Moreover, the length of the second rib 52 formed in the sixth point 60is set so that the second rib has an area C17 facing the first rib 51formed in the second point 54.

The lengths of the first and second ribs 51 and 52 formed in the thirdand seventh point 57 and 61 are set so that these first and second ribs51, 52 have areas C9, C10 facing each other along the arrangementdirection D2. The facing area C9 is disposed in the first rib 51 formedin the third point 57. The facing area C10 is disposed in the second rib52 formed in the seventh point 61.

The lengths of the second and first ribs 52 and 51 formed in the seventhand fifth point 61 and 59 are set so that these second and first ribs 52and 51 have areas C11, C12 facing each other along the arrangementdirection D2. The facing area C11 is disposed in the second rib 52formed in the seventh point 61. The facing area C12 is disposed in thefirst rib 51 formed in the fifth point 59.

The lengths of the first and second ribs 51 and 52 formed in the fifthand eighth point 59 and 62 are set so that these first and second ribs51, 52 have areas C13, C14 facing each other along the arrangementdirection D2. The facing area C13 is disposed in the first rib 51 formedin the fifth point 59. The facing area C14 is disposed in the second rib52 formed in the eighth point 62.

The lengths of the second and first ribs 52 and 51 formed in the eighthand fourth point 62 and 58 are set so that these second and first ribs52 and 51 have areas C15, C16 facing each other along the arrangementdirection D2. The facing area C15 is disposed in the second rib 52formed in the eighth point 62. The facing area C16 is disposed in thefirst rib 51 formed in the fourth point 58.

The facing mentioned in the present invention is a concept including acase where the respective first and second ribs 51, 52 are not parallelto each other as in the arrangement direction D2. Therefore, even whenthe respective first and second ribs 51, 52 are not parallel to eachother as in the first and second ribs 51, 52 formed in the cornerportion 28, these first and second ribs 51, 52 have areas facing eachother along the arrangement direction D2.

The first rib 51 is formed inwardly from the first rib 51 formed in thefourth point 58 along the upper rear wall 22 e. This first rib 51extends inwards. As shown in FIG. 4, a recessed portion 63 openingtoward the upper rear wall 22 e is formed in a region of the protrudingportion 28 a facing the upper rear wall 22 e.

The recessed portion 63 is used, for example, in disposing componentssuch as the PCB and the hard disk drive in the first housing 21 in thesame manner as in protrusion 45.

The recessed portion 63 has two arm portions 63 a, 63 b extending towardthe upper rear wall 22 e. In the present embodiment, these two armportions 63 a and 63 b are arranged, respectively, on, the side of thefirst rib 51 formed in the upper rear wall 22 e. Therefore, these twoarm portions 63 a, 63 b have functions of second ribs mentioned in thepresent invention.

Next, there will be described a behavior of the first housing 21 at atime when an impact is input into the portable computer 10 with respectto the protruding portion 28 a as one example.

For example, in a case where the portable computer 10 falls, when animpact having a value which is not less than a predetermined value isinput from the upper right wall 22 d in the region of the protrudingportion 28 a, a crack 70 is formed in the upper wall 22 a as shown by atwo-dot chain line in FIG. 5. The predetermined value is an unfavorablevalue for components such as the hard disk and the PCB contained in, forexample, the first housing 21.

The crack 70 winds its way to avoid tips of the first ribs 51 formed inthe first and second points 53 and 54, the second rib 52 formed on theprotrusion 45, and the second rib 52 formed on the vertical wall 46.

For example, even in a case where the impact having a value which is notless than the predetermined value is input into the corner portion 28,the crack formed in the upper wall 22 a of the corner portion 28 windsits way to avoid the first and second ribs 51, 52 formed in the cornerportion 28.

Note that as shown in FIG. 3, a plurality of first ribs 51 and aplurality of second ribs 52 are formed on the protruding portion 27 a inthe vicinity of the corner portion 27 in the upper cover 22 in the samemanner as in the protruding portion 28 a.

A vertical wall 71 is formed in a position facing the upper left wall 22c in the protruding portion 27 a. The vertical wall 71 is provided withtwo second ribs 52. These two second ribs 52 extend toward the upperleft wall 22 c.

Moreover, two first ribs 51 are formed in a region of the protrudingportion 27 a in the upper left wall 22 c. One of these two first ribs 51is formed in a ninth point 72. The first rib 51 formed in the ninthpoint 72 extends toward a point between two second ribs 52 formed on thevertical wall 71. The other first rib 51 is formed in a tenth point 73behind two second ribs 52 formed on the vertical wall 71.

The lengths of the first ribs 51 formed in the ninth and tenth pointsare determined depending on the strength required for the protrudingportion 28 a in the same manner as in the lengths of the first ribs 51formed in the first and second points 53 and 54.

The second rib 52 formed on the vertical wall 71 and the first ribs 51formed in the ninth and tenth points 72 and 73 are arranged so that thefirst and second ribs 51, 52 are alternately arranged. An arrangementdirection D3 of these first and second ribs 51, 52 is substantiallylinear.

The lengths of these first and second ribs 51, 52 are set so that theadjacent ribs have areas facing each other along the arrangementdirection D3. The lengths of the areas facing the first and second ribs51, 52 are set to be longer than halves of the lengths of the first andsecond ribs 51, 52 in the same manner as in the facing areas disposed inthe first and second ribs 51, 52 formed in the protruding portion 28 a.

Moreover, the corner portion 27 is provided with a boss portion 74having a function similar to that of the boss portion 43. The upper leftwall 22 c is gently bonded to the upper rear wall 22 e via a connectionportion 75. Although not shown, a plurality of second ribs 52 facing theconnection portion 75 may be formed in a region facing the connectionportion 75 connecting the upper left wall 22 c to the upper rear wall 22e in the peripheral face of the boss portion.

Furthermore, the connection portion 75 may have the first ribs 51 thatare provided on either of each second rib 52 formed on the boss portion74. A direction in which the first rib 51 formed on the connectionportion 75 and the second rib 52 formed on the boss portion 74 arearranged is substantially circular as in the arrangement direction D2.

The lengths of the first rib 51 formed on the connection portion 75 andthe second rib 52 formed on the boss portion 74 are set so that thefirst and second ribs 51, 52 disposed adjacent to each other in thearrangement direction have facing areas in a direction in which the ribsare arranged.

When the first and second ribs 51, 52 are formed in the protrudingportion 27 as described above, a crack formed by the impact within theprotruding portion 27 a of the upper wall 22 a winds its way to avoidthe first and second ribs 51, 52 in the same manner as in the crack 70.

Moreover, in the upper cover 22 of the present embodiment, the firstribs 51 are formed in portions other than the protruding portions 27 a,28 a in the upper left wall 22 c, the upper right wall 22 d, and theupper front wall 22 b. These first ribs 51 extend inwards.

In the portable computer 10 formed in this manner, as shown in FIG. 5,the crack 70 formed by the impact input into the first housing 21 windsits way. The crack 70 is formed in the first housing 21 to absorb theimpact. The length of the crack 70 is proportional to a size of impact.

That is, when the impact enlarges, the crack 70 lengthens. However, asdescribed above, when the first housing 21 is provided with thereinforcing structure including the first and second ribs 51, 52, thecrack 70 winds its way.

That is, even when the large impact is input to lengthen the crack 70,the crack 70 winds its way to minimize the region in which the crack 70is formed. Therefore, the region where the crack 70 is formed isminimized even after the impact having the value which is not less thanthe predetermined value is input into the first housing 21, and theappearance is therefore prevented from being worsened by the crack 70.

Moreover, by forming the plurality of first and second ribs 51, 52 areformed to broaden the region in which the crack 70 winds its way isbroaden.

Furthermore, the first rib 51 and the second rib 52 are arrangedalternately one by one, whereby the crack 70 effectively winds.

In addition, the protruding portions 25 a, 26 a, 27 a, and 28 a areformed in the first housing 21. Therefore, if the portable computer 10falls, the computer reaches the ground by any of the protruding portions25 a, 26 a, 27 a, and 28 a.

Moreover, the protruding portions 27 a, 28 a of the upper cover 22 areprovided with the reinforcing structure including the first and secondribs 51, 52, the region of the crack 70 formed by the impact input intothe first housing 21 is effectively minimized. Therefore, thedeterioration of the appearance of the first housing 21 is effectivelyinhibited.

Furthermore, the heights of the first and second ribs 51, 52 are largerthan the thicknesses of the upper wall 22 a in the vicinity of thepoints where the respective first and second ribs 51, 52 are formed.Consequently, the strengths of the first and second ribs 51, 52themselves are secured, and the first and second ribs 51, 52 are notdestroyed by the impact.

In other words, the crack 70 formed by the impact avoids the first andsecond ribs 51, 52, and winds its way without passing through the firstand second ribs 51, 52. Therefore, the region where the crack 70 isformed is effectively narrowed.

Moreover, in a case where the first and second ribs 51, 52 aresubstantially linearly arranged as in the arrangement direction D1, thelengths of these first and second ribs 51, 52 are set so that the lengthof each of the areas facing each other is larger than a half of thedistance between the areas. Specifically, a1>b1/2, a2>b2/2, and a3>b3/2are satisfied.

Therefore, the length of winding crack 70 is larger than a length about1.2 times that of the substantially linearly formed crack. Therefore,the region where the crack 70 is formed is effectively minimized.

Note that in the present embodiment, there has been describedrepresentatively the reinforcing structure including the first andsecond ribs 51, 52 disposed in the protruding portions 27 a, 28 a of theupper cover 22. However, the present invention is not limited to thisembodiment. For example, the reinforcing structure including the firstand second ribs 51, 52 may be formed in the protruding portions 25 a, 26a.

Moreover, in the present embodiment, there has been describedrepresentatively the reinforcing structure including the first andsecond ribs 51, 52 disposed in the upper cover 22. However the presentinvention is not limited to this embodiment. For example, thereinforcing structure including the first and second ribs 51, 52 may beformed in the lower cover 23. The reinforcing structure including thefirst and second ribs 51, 52 may be disposed in the second housing 31.

When the reinforcing structure including the first and second ribs 51,52 is disposed in the lower cover 23 and the second housing 31, thefirst rib 51 is formed inwardly from the side wall of the lower cover 23or the second housing 31. The second rib 52 is formed on the verticalwall disposed in the portion facing the portion provided with the firstrib 51 in the lower cover 23 or the second housing 31.

Note that the numbers and arrangements of the first and second ribs 51,52 used in the protruding portions 27 a, 28 a are illustrative and notrestrictive. Two first ribs 51 are formed within the region of theprotruding portion 28 a in the upper right wall 22 d, and each of theprotrusion 45 and the vertical wall 46 is provided with one second rib52. However three or four first ribs 51 may be formed on the upper rightwall 22d. Similarly, two or three second ribs 52 may be formed on theprotrusion 45 and the vertical wall 46. Accordingly, a plurality ofvertical walls may be formed and provided with the second ribs 52.

The number of the first or second ribs 51, 52 is determined depending onthe strength required for, for example, the first housing 21 or thesecond housing 31. In short, the first and second ribs 51, 52 arearranged in order along the direction in which they are arranged, andthe first and second ribs 51, 52 may only have the areas facing eachother along the arrangement direction.

The above description also applies to, for example, the corner portions25, 26, and 27, or the other protruding portions 25 a, 26 a, 27 a, and28 a.

Next, there will be described an electronic device in a secondembodiment of the present invention in accordance with a portablecomputer 10 as one example with reference to FIG. 8. Note that aconstitution having a function similar to that of the first embodimentis denoted with the same reference numerals and description is omitted.

The present embodiment is different from the first embodiment in alength of a second rib 52. This respect will be described specifically.

FIG. 8 shows a protruding portion 28 a of the present embodiment. In thepresent embodiment, there will be described first ribs 51 formed infirst and second points 53 and 54, and second ribs 52 formed on aprotrusion 45 and a vertical wall 46 with reference to FIG. 8.

In the present embodiment, the second ribs 52 formed on the protrusion45 and the vertical wall 46 extend immediately before an upper rightwall 22 d.

Moreover, since the second rib 52 extends immediately before the upperright wall 22 d, a deflection width of a crack 70 formed by an impactincreases. That is, a length of the crack 70 in a certain regionincreases. Therefore, a region where the crack 70 is formed iseffectively minimized.

Note that in the present embodiment, there have been describedrepresentatively the first and second ribs 51, 52 formed on the upperright wall 22 d, the protrusion 45, and the vertical wall 46 within theregion of the protruding portion 28 a. However the present invention isnot limited to this embodiment. For example, the ribs described abovemay be disposed in another portion of the upper cover 22, a lower cover23, or a second housing 31. The second rib 52 may extend immediatelybefore a side wall represented by the upper right wall 22 d as in thepresent embodiment.

Since the crack 70 largely winds its way in the region provided with thesecond rib 52 described in the present embodiment, the region providedwith the crack is effectively reduced in addition to the effect of thefirst embodiment.

Next, there will be described an electronic device in a third embodimentof the present invention in accordance with a portable computer 10 asone example with reference to FIG. 9. Noted that a constitution having afunction similar to that of the first embodiment is denoted with thesame reference numerals and description is omitted.

The present embodiment is different from the first embodiment in alength of a second rib 52. This respect will be described specifically.

In the present embodiment, there will be described representatively thefirst ribs 51 formed in first and second points 53 and 54 and secondribs 52 formed on a protrusion 45 and a vertical wall 46.

FIG. 9 shows a protruding portion 28 a of the present embodiment. In thepresent embodiment, as shown in FIG. 9, for example, the second rib 52formed on the vertical wall 46 is longer than the second rib 52 formedon the protrusion 45. In the present embodiment, an effect similar tothat of the first embodiment can be obtained.

Note that in the present embodiment, there have been describedrepresentatively the first ribs 51 formed in the first and second points53 and 54 and the second ribs 52 formed on the protrusion 45 and thevertical wall 46. However the present invention is not limited to thisembodiment.

For example, a reinforcing structure using the second ribs 52 havingdifferent lengths may be disposed in another portion of the upper cover22, a first housing 21, a lower cover 23, or a second housing 31 as inthe present embodiment. Even in this case, a similar effect is obtained.

Next, there will be described an electronic device in a fourthembodiment of the present invention in accordance with a portablecomputer 10 as one example with reference to FIG. 10. Note that aconstitution having a function similar to that of the first embodimentis denoted with the same reference numerals and description is omitted.

The present embodiment is different from the first embodiment in that aplurality of second ribs 52 are disposed between the first ribs 51disposed adjacent to each other in an arrangement direction. Thisrespect will be described specifically.

FIG. 10 shows a protruding portion 28 a of the present embodiment. Inthe present embodiment, there will be described representatively thefirst ribs 51 formed in first and second points 53 and 54 and secondribs 52 formed on a protrusion 45 and a vertical wall 46.

In the present embodiment, the second rib 52 formed on the protrusion 45is disposed between the first ribs 51 formed in the first and secondpoints 53 and 54. Even in the present embodiment, an effect similar tothat of the first embodiment can be obtained.

Note that in the present embodiment, two second ribs 52 are formedbetween the first ribs 51 formed in the first and second points 53 and54. However the present invention is not limited to this embodiment. Forexample, three or four second ribs 52 may be formed between the firstribs 51 formed in the first and second points 53 and 54.

Moreover, the reinforcing structure in which a plurality of second ribs52 are formed between the first ribs 51 disposed adjacent to each otherin an arrangement direction as described above is not limited to thatformed in the protruding portion 28 a. The reinforcing structure inwhich a plurality of second ribs 52 are formed between the first ribs 51disposed adjacent to each other may be formed in, for example, anotherportion of the upper cover 22, a lower cover 23, a second housing 31 orthe like.

In the present embodiment, there has been disclosed the reinforcingstructure in which a plurality of second ribs 52 are formed between thefirst ribs 51 disposed adjacent to each other. However, needless to say,a plurality of first rib 51 may be formed between the adjacent secondribs 52.

Next, there will be described an electronic device in a fifth embodimentof the present invention in accordance with a portable computer 10 asone example with reference to FIG. 11. Note that a constitution having afunction similar to that of the fourth embodiment is denoted with thesame reference numerals and description is omitted.

The present embodiment is different from the fourth embodiment inarrangement of second ribs 52 formed on a protrusion 45 and a verticalwall 46. This respect will be described specifically.

FIG. 11 shows an arrangement relation between first ribs 51 and thesecond ribs 52 in the protruding portion 28 a. As shown in FIG. 11, inthe present embodiment, the second rib 52 formed on the protrusion 45 isdisposed immediately beside the first rib 51 formed in a first point 53.The second rib 52 formed on the vertical wall 46 is disposed immediatelybeside the first rib 51 formed in a second point 54.

When each second rib 52 facing the first rib 51 in an arrangementdirection is disposed beside the facing first rib 51 as in the presentembodiment, a region of a crack 70 passing between the first and secondribs 51, 52 is substantially parallel to the first and second ribs 51,52. Therefore, the crack 70 lengthens in a region in the vicinity of thefirst and second ribs 51, 52 facing each other in the arrangementdirection. Therefore, in addition to an effect of the fourth embodiment,the region where the crack 70 is formed is minimized.

Next, there will be described an electronic device in a sixth embodimentof the present invention in accordance with a portable computer 10 asone example with reference to FIG. 12. Note that a constitution having afunction similar to that of the fourth embodiment is denoted with thesame reference numerals and description is omitted.

The present embodiment is different from the fourth embodiment inlengths and arrangements of a plurality of second ribs 52 disposedbetween first ribs 51 disposed adjacent to each other along a directionin which the plurality of first and second ribs 51, 52 are arranged.This respect will be described specifically.

In the present embodiment, the second ribs 52 disposed between first andsecond points 53 and 54 are formed and arranged to bring a position of acrack 70 formed by an impact to an arbitrary position.

Specifically, as shown in FIG. 12, for example, five second ribs 52 areformed between the first and second points 53 and 54. Among these fivesecond ribs 52, three second ribs 52 are formed on a protrusion 45. Tworemaining second ribs 52 are formed on a vertical wall 46.

Among three second ribs 52 formed on the protrusion 45, the second rib52 disposed rearward extend to a position immediately before an upperright wall 22 d. The lengths of the second ribs 52 disposed on oppositesides of the second rib 52 gradually shorten toward the first ribs 51formed in the first and second points 53 and 54.

A shape formed by connecting tips of the second ribs 52 formed in thismanner is a mountain shape protruding toward an upper right wall 22 d.

Therefore, a shape of the crack 70 formed by the impact is a mountainshape protruding toward the upper right wall 22 d as shown by a two-dotchain line in the drawing.

In the present embodiment, a plurality of second ribs 52 bring the crack70 into a large mountain shape. However the present invention is notlimited to this embodiment.

Since the lengths or the arrangement of the second ribs 52 are setarbitrarily, in addition to an effect of the fourth embodiment, theshape of the crack 70 formed by the impact can be set to be arbitrary.

Next, there will be described an electronic device in a seventhembodiment of the present invention in accordance with a portablecomputer 10 as one example with reference to FIGS. 13 and 14. Note thata constitution having a function similar to that of the first embodimentis denoted with the same reference numerals and description is omitted.

The present embodiment is different from the first embodiment in regionsin which first and second ribs 51, 52 are formed. This respect will bedescribed specifically.

As shown in FIG. 13, in the present embodiment, the first and secondribs 51, 52 are formed over the substantially whole region of a sidewall of an upper cover 22, that is, an upper front wall 22 b, an upperleft wall 22 c, an upper right wall 22 d, and an upper rear wall 22 e.

Note that a cover member 80 is separately attached to the inside of arear end of the upper cover 22 in a width direction. Therefore, even ifthe portable computer falls, an impact is not easily input into theinside of the rear end of the portable computer 10.

Therefore, in the present embodiment, any of the first and second ribs51, 52 is not formed in inner portions 81 along the upper rear wall 22 ein protruding portions 27 a, 28 a. However, the present invention is notlimited to this embodiment. For example, the first and second ribs 51,52 may be formed in the inner portions 81 along the upper rear wall 22 ein the protruding portions 27 a, 28 a.

Moreover, shown in FIG. 14, in a case where the upper rear wall 22 eextends in the width direction as shown by a two-dot chain line in thedrawing without using the cover member 80, the first and second ribs 51,52 may be formed along the upper rear wall 22 e as shown by a two-dotchain line.

As shown in FIGS. 13 and 14, in the present embodiment, the first andsecond ribs 51, 52 are alternately arranged along a peripheral wall.However, the present invention is not limited to this embodiment. Forexample, partially as described in the fourth to sixth embodiments, aplurality of second ribs 52 may be formed between the adjacent firstribs 51 along the peripheral wall. Note that a direction D4 along theperipheral wall, that is, the upper front wall 22 b, the upper left wall22 c, the upper right wall 22 d, and the upper rear wall 22 e is adirection in which the first and second ribs 51, 52 are arranged asmentioned in the present invention.

In the present embodiment, the strength of the upper cover 22 isenhanced.

Note that the first and second ribs 51, 52 may be formed in thesubstantially whole area of the side wall of a lower cover 23, that is,a lower front wall 23 b, a lower left wall 23 c, a lower right wall 23d, and a lower rear wall 23 e. In this case, the strength of the lowercover 23 is enhanced. The first and second ribs 51, 52 may be formedover the substantially whole area of a side wall of a second housing 31.In this case, the strength of the second housing 31 is enhanced.

Moreover, in the present invention, the first to seventh embodimentshave been described by use of the portable computer 10. However, thepresent invention is not limited to this example. The present inventionmay be used in, for example, a case of a battery pack as one example ofthe electronic device.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the inventions. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the inventions. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the inventions.

1. An electronic device comprising: a housing; and a circuit boardcontained in the housing; the housing including; a main wall; a sidewall integrally formed with the main wall; a vertical wall integrallyformed with the main wall, and facing to the side wall; a first ribintegrally formed with the side wall and the main wall and extendingfrom the side wall toward the vertical wall, the first rib having afirst end portion separated from the vertical wall; and a second ribintegrally formed with the vertical wall and the main wall and extendingfrom the vertical wall toward the side wall, the second rib having asecond end portion separated from the side wall and facing to the firstend portion.
 2. The electronic device according to claim 1, wherein theplurality of first and second ribs are formed.
 3. The electronic deviceaccording to claim 2, wherein at least a part of the plurality of firstand second ribs are arranged alternately one by one in the arrangementdirection.
 4. The electronic device according to claim 3, wherein atleast a pair of second ribs disposed adjacent to each other via thefirst rib in the arrangement direction have mutually different lengths.5. The electronic device according to claim 2, wherein the plurality ofsecond ribs are arranged in a region between the first ribs disposedadjacent to each other in the arrangement direction.
 6. The electronicdevice according to claim 5, wherein the second rib disposed adjacent tothe first rib along the arrangement direction is disposed on the side ofthe first rib.
 7. The electronic device according to claim 5, whereinlengths of the plurality of second ribs arranged in a region between thefirst ribs disposed adjacent to each other along the arrangementdirection depend on a position of a crack to be formed in the main wall.8. The electronic device according to claim 1, wherein heights of thefirst and second ribs are larger than a thickness of the main wall in apoint where these first and second ribs are formed.
 9. The electronicdevice according to claim 1, wherein the housing is provided with aprotruding portion protruding toward outside, and the first and secondribs are formed in the protruding portion.
 10. The electronic deviceaccording to claim 2, wherein the plurality of first and second ribs areformed in the substantially whole region of the side wall.
 11. Theelectronic device according to claim 1, wherein the arrangementdirection is linear, and a length of the facing area is larger than ahalf of a distance between the first rib and the second rib disposedadjacent to each other along the arrangement direction.